Vertical axis wind turbine (VAWT) uses the wind turbine rotor with multiple blades and an axis perpendicular to the ground. The main advantage of VAWT is that VAWT can extract energy of wind streaming from any directions; therefore, VAWT performs better in turbulence than horizontal axis wind turbine (HAWT).
Wind turbine rotor is one of the most important components of VAWT. The blade geometry of the wind turbine rotor will directly affect the power efficiency of VAWT. The wind turbine rotor with higher rotational inertia is better at reducing the shaking and vibration of the wind turbine rotor caused by the turbulence while requiring a higher wind speed and torque for starting and activating. On the other hand, the wind turbine rotor with lower rotational inertia is easily affected by turbulence on the rotation stability while the advantage is easy to activate.
The theoretic value of the equivalent rotational inertia is
  I  =            1      2        ⁢          MR      2      or I=MR2, where M is the mass of wind turbine rotor, and R is the radius of the wind turbine rotor.
Therefore, increasing the rotational inertia of the wind turbine rotor can be achieved by increasing the mass or the radius of the wind turbine rotor. However, VAWT needs a higher start-up wind speed for the wind turbine rotor with a bigger mass. And, increasing the radius of the wind turbine rotor will cause constraint to VAWT products designed for applications. Therefore, it is imperative to devise a stabilizing apparatus to be used with the original design and structure of a wind turbine rotor so as to automatically change the rotational inertia of the wind turbine rotor to achieve the objectives of requiring a lower start-up wind speed, and maintaining and stabilizing the rotor rotation speed.